fs/autofs4/waitq.c

   1 /*
   2  * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
   3  * Copyright 2001-2006 Ian Kent <raven@themaw.net>
   4  *
   5  * This file is part of the Linux kernel and is made available under
   6  * the terms of the GNU General Public License, version 2, or at your
   7  * option, any later version, incorporated herein by reference.
   8  */
   9
  10 #include <linux/slab.h>
  11 #include <linux/time.h>
  12 #include <linux/signal.h>
  13 #include <linux/sched/signal.h>
  14 #include <linux/file.h>
  15 #include "autofs_i.h"
  16
  17 /* We make this a static variable rather than a part of the superblock; it
  18  * is better if we don't reassign numbers easily even across filesystems
  19  */
  20 static autofs_wqt_t autofs4_next_wait_queue = 1;
  21
  22 /* These are the signals we allow interrupting a pending mount */
  23 #define SHUTDOWN_SIGS   (sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))
  24
  25 void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
  26 {
  27         struct autofs_wait_queue *wq, *nwq;
  28
  29         mutex_lock(&sbi->wq_mutex);
  30         if (sbi->catatonic) {
  31                 mutex_unlock(&sbi->wq_mutex);
  32                 return;
  33         }
  34
  35         pr_debug("entering catatonic mode\n");
  36
  37         sbi->catatonic = 1;
  38         wq = sbi->queues;
  39         sbi->queues = NULL;     /* Erase all wait queues */
  40         while (wq) {
  41                 nwq = wq->next;
  42                 wq->status = -ENOENT; /* Magic is gone - report failure */
  43                 kfree(wq->name.name);
  44                 wq->name.name = NULL;
  45                 wq->wait_ctr--;
  46                 wake_up_interruptible(&wq->queue);
  47                 wq = nwq;
  48         }
  49         fput(sbi->pipe);        /* Close the pipe */
  50         sbi->pipe = NULL;
  51         sbi->pipefd = -1;
  52         mutex_unlock(&sbi->wq_mutex);
  53 }
  54
  55 static int autofs4_write(struct autofs_sb_info *sbi,
  56                          struct file *file, const void *addr, int bytes)
  57 {
  58         unsigned long sigpipe, flags;
  59         mm_segment_t fs;
  60         const char *data = (const char *)addr;
  61         ssize_t wr = 0;
  62
  63         sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  64
  65         /* Save pointer to user space and point back to kernel space */
  66         fs = get_fs();
  67         set_fs(KERNEL_DS);
  68
  69         mutex_lock(&sbi->pipe_mutex);
  70         while (bytes) {
  71                 wr = __vfs_write(file, data, bytes, &file->f_pos);
  72                 if (wr <= 0)
  73                         break;
  74                 data += wr;
  75                 bytes -= wr;
  76         }
  77         mutex_unlock(&sbi->pipe_mutex);
  78
  79         set_fs(fs);
  80
  81         /* Keep the currently executing process from receiving a
  82          * SIGPIPE unless it was already supposed to get one
  83          */
  84         if (wr == -EPIPE && !sigpipe) {
  85                 spin_lock_irqsave(&current->sighand->siglock, flags);
  86                 sigdelset(&current->pending.signal, SIGPIPE);
  87                 recalc_sigpending();
  88                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
  89         }
  90
  91         return (bytes > 0);
  92 }
  93
  94 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
  95                                  struct autofs_wait_queue *wq,
  96                                  int type)
  97 {
  98         union {
  99                 struct autofs_packet_hdr hdr;
 100                 union autofs_packet_union v4_pkt;
 101                 union autofs_v5_packet_union v5_pkt;
 102         } pkt;
 103         struct file *pipe = NULL;
 104         size_t pktsz;
 105
 106         pr_debug("wait id = 0x%08lx, name = %.*s, type=%d\n",
 107                  (unsigned long) wq->wait_queue_token,
 108                  wq->name.len, wq->name.name, type);
 109
 110         memset(&pkt, 0, sizeof(pkt)); /* For security reasons */
 111
 112         pkt.hdr.proto_version = sbi->version;
 113         pkt.hdr.type = type;
 114
 115         switch (type) {
 116         /* Kernel protocol v4 missing and expire packets */
 117         case autofs_ptype_missing:
 118         {
 119                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
 120
 121                 pktsz = sizeof(*mp);
 122
 123                 mp->wait_queue_token = wq->wait_queue_token;
 124                 mp->len = wq->name.len;
 125                 memcpy(mp->name, wq->name.name, wq->name.len);
 126                 mp->name[wq->name.len] = '\0';
 127                 break;
 128         }
 129         case autofs_ptype_expire_multi:
 130         {
 131                 struct autofs_packet_expire_multi *ep =
 132                                         &pkt.v4_pkt.expire_multi;
 133
 134                 pktsz = sizeof(*ep);
 135
 136                 ep->wait_queue_token = wq->wait_queue_token;
 137                 ep->len = wq->name.len;
 138                 memcpy(ep->name, wq->name.name, wq->name.len);
 139                 ep->name[wq->name.len] = '\0';
 140                 break;
 141         }
 142         /*
 143          * Kernel protocol v5 packet for handling indirect and direct
 144          * mount missing and expire requests
 145          */
 146         case autofs_ptype_missing_indirect:
 147         case autofs_ptype_expire_indirect:
 148         case autofs_ptype_missing_direct:
 149         case autofs_ptype_expire_direct:
 150         {
 151                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 152                 struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
 153
 154                 pktsz = sizeof(*packet);
 155
 156                 packet->wait_queue_token = wq->wait_queue_token;
 157                 packet->len = wq->name.len;
 158                 memcpy(packet->name, wq->name.name, wq->name.len);
 159                 packet->name[wq->name.len] = '\0';
 160                 packet->dev = wq->dev;
 161                 packet->ino = wq->ino;
 162                 packet->uid = from_kuid_munged(user_ns, wq->uid);
 163                 packet->gid = from_kgid_munged(user_ns, wq->gid);
 164                 packet->pid = wq->pid;
 165                 packet->tgid = wq->tgid;
 166                 break;
 167         }
 168         default:
 169                 pr_warn("bad type %d!\n", type);
 170                 mutex_unlock(&sbi->wq_mutex);
 171                 return;
 172         }
 173
 174         pipe = get_file(sbi->pipe);
 175
 176         mutex_unlock(&sbi->wq_mutex);
 177
 178         if (autofs4_write(sbi, pipe, &pkt, pktsz))
 179                 autofs4_catatonic_mode(sbi);
 180         fput(pipe);
 181 }
 182
 183 static int autofs4_getpath(struct autofs_sb_info *sbi,
 184                            struct dentry *dentry, char **name)
 185 {
 186         struct dentry *root = sbi->sb->s_root;
 187         struct dentry *tmp;
 188         char *buf;
 189         char *p;
 190         int len;
 191         unsigned seq;
 192
 193 rename_retry:
 194         buf = *name;
 195         len = 0;
 196
 197         seq = read_seqbegin(&rename_lock);
 198         rcu_read_lock();
 199         spin_lock(&sbi->fs_lock);
 200         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 201                 len += tmp->d_name.len + 1;
 202
 203         if (!len || --len > NAME_MAX) {
 204                 spin_unlock(&sbi->fs_lock);
 205                 rcu_read_unlock();
 206                 if (read_seqretry(&rename_lock, seq))
 207                         goto rename_retry;
 208                 return 0;
 209         }
 210
 211         *(buf + len) = '\0';
 212         p = buf + len - dentry->d_name.len;
 213         strncpy(p, dentry->d_name.name, dentry->d_name.len);
 214
 215         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 216                 *(--p) = '/';
 217                 p -= tmp->d_name.len;
 218                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
 219         }
 220         spin_unlock(&sbi->fs_lock);
 221         rcu_read_unlock();
 222         if (read_seqretry(&rename_lock, seq))
 223                 goto rename_retry;
 224
 225         return len;
 226 }
 227
 228 static struct autofs_wait_queue *
 229 autofs4_find_wait(struct autofs_sb_info *sbi, const struct qstr *qstr)
 230 {
 231         struct autofs_wait_queue *wq;
 232
 233         for (wq = sbi->queues; wq; wq = wq->next) {
 234                 if (wq->name.hash == qstr->hash &&
 235                     wq->name.len == qstr->len &&
 236                     wq->name.name &&
 237                     !memcmp(wq->name.name, qstr->name, qstr->len))
 238                         break;
 239         }
 240         return wq;
 241 }
 242
 243 /*
 244  * Check if we have a valid request.
 245  * Returns
 246  * 1 if the request should continue.
 247  *   In this case we can return an autofs_wait_queue entry if one is
 248  *   found or NULL to idicate a new wait needs to be created.
 249  * 0 or a negative errno if the request shouldn't continue.
 250  */
 251 static int validate_request(struct autofs_wait_queue **wait,
 252                             struct autofs_sb_info *sbi,
 253                             const struct qstr *qstr,
 254                             const struct path *path, enum autofs_notify notify)
 255 {
 256         struct dentry *dentry = path->dentry;
 257         struct autofs_wait_queue *wq;
 258         struct autofs_info *ino;
 259
 260         if (sbi->catatonic)
 261                 return -ENOENT;
 262
 263         /* Wait in progress, continue; */
 264         wq = autofs4_find_wait(sbi, qstr);
 265         if (wq) {
 266                 *wait = wq;
 267                 return 1;
 268         }
 269
 270         *wait = NULL;
 271
 272         /* If we don't yet have any info this is a new request */
 273         ino = autofs4_dentry_ino(dentry);
 274         if (!ino)
 275                 return 1;
 276
 277         /*
 278          * If we've been asked to wait on an existing expire (NFY_NONE)
 279          * but there is no wait in the queue ...
 280          */
 281         if (notify == NFY_NONE) {
 282                 /*
 283                  * Either we've betean the pending expire to post it's
 284                  * wait or it finished while we waited on the mutex.
 285                  * So we need to wait till either, the wait appears
 286                  * or the expire finishes.
 287                  */
 288
 289                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 290                         mutex_unlock(&sbi->wq_mutex);
 291                         schedule_timeout_interruptible(HZ/10);
 292                         if (mutex_lock_interruptible(&sbi->wq_mutex))
 293                                 return -EINTR;
 294
 295                         if (sbi->catatonic)
 296                                 return -ENOENT;
 297
 298                         wq = autofs4_find_wait(sbi, qstr);
 299                         if (wq) {
 300                                 *wait = wq;
 301                                 return 1;
 302                         }
 303                 }
 304
 305                 /*
 306                  * Not ideal but the status has already gone. Of the two
 307                  * cases where we wait on NFY_NONE neither depend on the
 308                  * return status of the wait.
 309                  */
 310                 return 0;
 311         }
 312
 313         /*
 314          * If we've been asked to trigger a mount and the request
 315          * completed while we waited on the mutex ...
 316          */
 317         if (notify == NFY_MOUNT) {
 318                 struct dentry *new = NULL;
 319                 struct path this;
 320                 int valid = 1;
 321
 322                 /*
 323                  * If the dentry was successfully mounted while we slept
 324                  * on the wait queue mutex we can return success. If it
 325                  * isn't mounted (doesn't have submounts for the case of
 326                  * a multi-mount with no mount at it's base) we can
 327                  * continue on and create a new request.
 328                  */
 329                 if (!IS_ROOT(dentry)) {
 330                         if (d_unhashed(dentry) &&
 331                             d_really_is_positive(dentry)) {
 332                                 struct dentry *parent = dentry->d_parent;
 333
 334                                 new = d_lookup(parent, &dentry->d_name);
 335                                 if (new)
 336                                         dentry = new;
 337                         }
 338                 }
 339                 this.mnt = path->mnt;
 340                 this.dentry = dentry;
 341                 if (path_has_submounts(&this))
 342                         valid = 0;
 343
 344                 if (new)
 345                         dput(new);
 346                 return valid;
 347         }
 348
 349         return 1;
 350 }
 351
 352 int autofs4_wait(struct autofs_sb_info *sbi,
 353                  const struct path *path, enum autofs_notify notify)
 354 {
 355         struct dentry *dentry = path->dentry;
 356         struct autofs_wait_queue *wq;
 357         struct qstr qstr;
 358         char *name;
 359         int status, ret, type;
 360         pid_t pid;
 361         pid_t tgid;
 362
 363         /* In catatonic mode, we don't wait for nobody */
 364         if (sbi->catatonic)
 365                 return -ENOENT;
 366
 367         /*
 368          * Try translating pids to the namespace of the daemon.
 369          *
 370          * Zero means failure: we are in an unrelated pid namespace.
 371          */
 372         pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 373         tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 374         if (pid == 0 || tgid == 0)
 375                 return -ENOENT;
 376
 377         if (d_really_is_negative(dentry)) {
 378                 /*
 379                  * A wait for a negative dentry is invalid for certain
 380                  * cases. A direct or offset mount "always" has its mount
 381                  * point directory created and so the request dentry must
 382                  * be positive or the map key doesn't exist. The situation
 383                  * is very similar for indirect mounts except only dentrys
 384                  * in the root of the autofs file system may be negative.
 385                  */
 386                 if (autofs_type_trigger(sbi->type))
 387                         return -ENOENT;
 388                 else if (!IS_ROOT(dentry->d_parent))
 389                         return -ENOENT;
 390         }
 391
 392         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 393         if (!name)
 394                 return -ENOMEM;
 395
 396         /* If this is a direct mount request create a dummy name */
 397         if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
 398                 qstr.len = sprintf(name, "%p", dentry);
 399         else {
 400                 qstr.len = autofs4_getpath(sbi, dentry, &name);
 401                 if (!qstr.len) {
 402                         kfree(name);
 403                         return -ENOENT;
 404                 }
 405         }
 406         qstr.name = name;
 407         qstr.hash = full_name_hash(dentry, name, qstr.len);
 408
 409         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 410                 kfree(qstr.name);
 411                 return -EINTR;
 412         }
 413
 414         ret = validate_request(&wq, sbi, &qstr, path, notify);
 415         if (ret <= 0) {
 416                 if (ret != -EINTR)
 417                         mutex_unlock(&sbi->wq_mutex);
 418                 kfree(qstr.name);
 419                 return ret;
 420         }
 421
 422         if (!wq) {
 423                 /* Create a new wait queue */
 424                 wq = kmalloc(sizeof(struct autofs_wait_queue), GFP_KERNEL);
 425                 if (!wq) {
 426                         kfree(qstr.name);
 427                         mutex_unlock(&sbi->wq_mutex);
 428                         return -ENOMEM;
 429                 }
 430
 431                 wq->wait_queue_token = autofs4_next_wait_queue;
 432                 if (++autofs4_next_wait_queue == 0)
 433                         autofs4_next_wait_queue = 1;
 434                 wq->next = sbi->queues;
 435                 sbi->queues = wq;
 436                 init_waitqueue_head(&wq->queue);
 437                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
 438                 wq->dev = autofs4_get_dev(sbi);
 439                 wq->ino = autofs4_get_ino(sbi);
 440                 wq->uid = current_cred()->uid;
 441                 wq->gid = current_cred()->gid;
 442                 wq->pid = pid;
 443                 wq->tgid = tgid;
 444                 wq->status = -EINTR; /* Status return if interrupted */
 445                 wq->wait_ctr = 2;
 446
 447                 if (sbi->version < 5) {
 448                         if (notify == NFY_MOUNT)
 449                                 type = autofs_ptype_missing;
 450                         else
 451                                 type = autofs_ptype_expire_multi;
 452                 } else {
 453                         if (notify == NFY_MOUNT)
 454                                 type = autofs_type_trigger(sbi->type) ?
 455                                         autofs_ptype_missing_direct :
 456                                          autofs_ptype_missing_indirect;
 457                         else
 458                                 type = autofs_type_trigger(sbi->type) ?
 459                                         autofs_ptype_expire_direct :
 460                                         autofs_ptype_expire_indirect;
 461                 }
 462
 463                 pr_debug("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 464                          (unsigned long) wq->wait_queue_token, wq->name.len,
 465                          wq->name.name, notify);
 466
 467                 /*
 468                  * autofs4_notify_daemon() may block; it will unlock ->wq_mutex
 469                  */
 470                 autofs4_notify_daemon(sbi, wq, type);
 471         } else {
 472                 wq->wait_ctr++;
 473                 pr_debug("existing wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 474                          (unsigned long) wq->wait_queue_token, wq->name.len,
 475                          wq->name.name, notify);
 476                 mutex_unlock(&sbi->wq_mutex);
 477                 kfree(qstr.name);
 478         }
 479
 480         /*
 481          * wq->name.name is NULL iff the lock is already released
 482          * or the mount has been made catatonic.
 483          */
 484         if (wq->name.name) {
 485                 /* Block all but "shutdown" signals while waiting */
 486                 unsigned long shutdown_sigs_mask;
 487                 unsigned long irqflags;
 488                 sigset_t oldset;
 489
 490                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 491                 oldset = current->blocked;
 492                 shutdown_sigs_mask = SHUTDOWN_SIGS & ~oldset.sig[0];
 493                 siginitsetinv(&current->blocked, shutdown_sigs_mask);
 494                 recalc_sigpending();
 495                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 496
 497                 wait_event_interruptible(wq->queue, wq->name.name == NULL);
 498
 499                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 500                 current->blocked = oldset;
 501                 recalc_sigpending();
 502                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 503         } else {
 504                 pr_debug("skipped sleeping\n");
 505         }
 506
 507         status = wq->status;
 508
 509         /*
 510          * For direct and offset mounts we need to track the requester's
 511          * uid and gid in the dentry info struct. This is so it can be
 512          * supplied, on request, by the misc device ioctl interface.
 513          * This is needed during daemon resatart when reconnecting
 514          * to existing, active, autofs mounts. The uid and gid (and
 515          * related string values) may be used for macro substitution
 516          * in autofs mount maps.
 517          */
 518         if (!status) {
 519                 struct autofs_info *ino;
 520                 struct dentry *de = NULL;
 521
 522                 /* direct mount or browsable map */
 523                 ino = autofs4_dentry_ino(dentry);
 524                 if (!ino) {
 525                         /* If not lookup actual dentry used */
 526                         de = d_lookup(dentry->d_parent, &dentry->d_name);
 527                         if (de)
 528                                 ino = autofs4_dentry_ino(de);
 529                 }
 530
 531                 /* Set mount requester */
 532                 if (ino) {
 533                         spin_lock(&sbi->fs_lock);
 534                         ino->uid = wq->uid;
 535                         ino->gid = wq->gid;
 536                         spin_unlock(&sbi->fs_lock);
 537                 }
 538
 539                 if (de)
 540                         dput(de);
 541         }
 542
 543         /* Are we the last process to need status? */
 544         mutex_lock(&sbi->wq_mutex);
 545         if (!--wq->wait_ctr)
 546                 kfree(wq);
 547         mutex_unlock(&sbi->wq_mutex);
 548
 549         return status;
 550 }
 551
 552
 553 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 554 {
 555         struct autofs_wait_queue *wq, **wql;
 556
 557         mutex_lock(&sbi->wq_mutex);
 558         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 559                 if (wq->wait_queue_token == wait_queue_token)
 560                         break;
 561         }
 562
 563         if (!wq) {
 564                 mutex_unlock(&sbi->wq_mutex);
 565                 return -EINVAL;
 566         }
 567
 568         *wql = wq->next;        /* Unlink from chain */
 569         kfree(wq->name.name);
 570         wq->name.name = NULL;   /* Do not wait on this queue */
 571         wq->status = status;
 572         wake_up_interruptible(&wq->queue);
 573         if (!--wq->wait_ctr)
 574                 kfree(wq);
 575         mutex_unlock(&sbi->wq_mutex);
 576
 577         return 0;
 578 }